1. Field of the Invention
The present invention relates to a die holding mechanism which picks up a die formed with connecting wires thereon and to a die packing device which accommodate a die in a tray and further to a die bonding apparatus which bonds a die to a substrate.
2. Prior Art
In recent years, semiconductor devices equipped with dies, which have connecting wires for absorbing the difference in thermal expansion between the die and the substrate, have been developed.
More specifically, as seen from FIG. 5(a), a die 1 is provided with connecting wires 2, and solder bumps 4 are formed by printing on a substrate 3 at positions that correspond to the connecting wires 2. A semiconductor device 5 is made by bonding the connecting wires 2 of the die 1 to the solder bumps 4 of the substrate 3 as shown in FIG. 5(b). In such a semiconductor device 5, the difference in thermal expansion between the die 1 and the substrate 3 is absorbed by the connecting wires 2.
In the above-described die 1, the connecting wires 2 are formed by a wire bonding method when the die 1 is in a state of wafer as shown in FIG. 6. After the wires are formed, a wafer 7 is pasted to a wafer sheet 6 and then finely divided in the longitudinal and lateral directions. An individual die 1 is thus obtained. The die is sent to a next process xe2x80x9cas isxe2x80x9d in this state, or it is sent to the next process after the wafer sheet 6 is expanded so that the gaps between the dies 1 are widened. In some cases, the wafer 7 is pasted to the wafer sheet 6, and then connecting wires 2 are formed by wire bonding.
When the die 1 thus pasted with the wafer sheet 6 is packed in a tray or bonded to a substrate 3, it is necessary to pick up the die 1 from the wafer sheet 6 by a die holding mechanism.
In one of conventional die holding mechanisms, the vacuum suction surface of a vacuum suction nozzle that vacuum-chucks a die 1 is formed flat. This is disclosed in Japanese Patent Application Publication (Kokoku) No. S61-32813. The vacuum suction surface can be formed as a pyramidal surface as shown in, for instance, Japanese Patent Application Publication (Kokoku) No. H3-54858. Japanese Patent Application Laid-Open (Kokai) No. H8-130230 and Japanese Patent No. 2725701, for instance, disclose mechanisms in which a die picked up by a die holding mechanism is inverted or brought upside-down and bonded to a substrate.
However, in the above prior art, if a die is provided with connecting wires, such a die cannot be vacuum-suctioned by the flat type vacuum suction nozzle. In the case of a pyramidal vacuum suction nozzle, the pyramidal surface contacts the connecting wires and causes deformation in the connecting wires. Furthermore, the die tends drop from the pyramidal surface by the spring force of the connecting wires. Accordingly, a die is not held well by vacuum suction that uses a pyramidal vacuum suction nozzle, either.
Thus, the question has been how to pickup a die that has connecting wires thereon from a wafer sheet.
Accordingly, the object of the present invention is to provide a die holding mechanism which can pick up a die from a wafer sheet without deforming the connecting wires provided on the die.
Another object of the present invention is to provide a die packing device that packs a die in a tray using (a part of) the die holding mechanism.
Still another object of the present invention is to provide a die bonding apparatus that bonds a die to a substrate using (a part of) the die holding mechanism.
The above object is accomplished by a unique structure of the present invention for a die holding mechanism that comprises a die push-up means for pushing up a die placed on a wafer sheet and a die holding means for holding the die pushed up by the die push-up means; and in the present invention,
the die is provided with wires on an upper surface thereof;
the die holding means comprises:
a connecting wire receiving shaft which is installed so as to be moved up and down,
a pair of die holding levers which have die holding sections for holding a die and are installed on both sides of the connecting wire receiving shaft so as to open and close, and
a die holding lever opening-and-closing means which opens and closes the die holding levers; and wherein
the die is pushed upward by a push-up needle of the die push-up means, and the connecting wire receiving shaft is pushed upward by the die during the upward movement of the die; and when the connecting wire receiving shaft is raised by a predetermined amount by the die being pushed upward, the die holding levers of the die holding means are closed, so that the die holding sections of the die holding levers hold the die, and thereafter the push-up needle of the die push-up means is lowered, thus allowing the die to be held by the die holding levers.
In the above structure, when the die holding levers hold the die, the die holding sections of the die holding levers are brought beneath the undersurface of the die or brought to the side surfaces of the die.
Furthermore, the die packing device of the present invention is characterized in that the die packing device uses the die holding means describe above in such a manner that the die holding means is installed so as to be movable up and down and moved to above a tray in which dies are to be packed, and a collet which is rotatable and holds a die by vacuum suction is installed above the tray, so that the collet receives the die from the die holding means, inverts the die so as to cause the connecting wires to face down, and then causes the die to be accommodated in the tray.
The die bonding apparatus of the present invention is characterized in that the die bonding apparatus uses the die holding means described above in such a manner that the die holding means is installed so as to be movable up and down and moved to above a substrate to which a die is to be bonded, and a collet which is rotatable and holds a die by vacuum suction is installed above the substrate, so that the collet receives the die from the die holding means, inverts the die so as to cause the connecting wires of the die to face downward, and then causes the die to be bonded to the substrate.